Least count of a spectrometer = value of the smallest division on the main scale or vernier scale
Least count = value of 1 main scale division รท total number of vernier scale divisions
Least count = difference between the value of 1 main scale division and 1 vernier scale division
Formula: LC = 1 MSD / n
Formula: LC = 1 MSD – 1 VSD
If 1 MSD = 1 degree and vernier has 30 divisions, LC = 1/30 degree
Convert the result into minutes or seconds if needed
Standard spectrometer least count is often 1 minute of arc
To find the least count, note the main scale value and the number of vernier divisions
Apply the formula and simplify the result